Diuretics Flashcards
Thiazide and related diuretics
Hydrochlorothiazide
Chlorthalidone
Indapamide
Metolazone
Thiazide and related diuretics - MoA
Acts on early portion of the distal tubule to inhibit the Na+, Cl- symporter that participates in the reabsorption of sodium and chloride from this segment of the nephron. This action leads to the delivery of a greater volume of sodium and chloride-enriched tubular fluid to the late distal tubule and collecting duct, which in turn stimulates the exchange of sodium and potassium at these sites. In this process a small amount of potassium is secreted into urine in the tubules –> kaliuretic effect; can cause hypokalemia. Thiazide also increase magnesium excretion, but decrease calcium excretion in the urine.
Decrease Ca excretion result from decreased expression of Ca transport proteins (epithelial Ca channel calbindin, sodium-calcium exchanger protein) in renal tubules after thiazide adm.
Thiazide and related diuretic - Clinical use
Hypertension
Edema associated with heart failure, cirrhosis, corticosteroid therapy, estrogen therapy.
Renal disorders such as nephrotic syndrome
Nephrogenic diabetes insipidus (decrease excessive urine V dramatically, reduction in plasma V –> increase Na&water reabsorption from proximal tubule –> less water delivered to diluting segments of nephron)
Nephrolithiasis (kidney stones) –> reduces Ca excretion
Thiazide and related diuretic - Adverse effects
Hypokalemia –> hypokalemic metabolic alkalosis
Hyponatermia
Hypomagnesemia
Hyperglycemia
Hyperlipidemia
Hyperuricemia –> can lead to gout
Hypercalcemia
Decreases the insulin sensitivity –> can cause diabetes in some pat.
Thiazide-induced hypokalemia can decrease insulin secretion.
Blood cell deficiencies
Thiazide and related diuretic - Interactions and Contraindication
Interactions:
Potentiated the diuretic effect of loop diuretics
Contraindications: Hypotension Sulfa-allergy Gout Renal failure Lithium therapy Hypokalemia May worsen diabetes
Which is the most frequently used thiazide diuretic?
Hydrochlorothiazide
Loop diuretics
Furosemide
Bumetanide
Torsemide
Ethacrynic acid
Loop diuretics - MoA
Inhibit the Na+, K+, 2Cl- symporter in the ascending limb of loop of Henle and thereby exert a powerful natriuretic effect. Inhibit the reabsorption of a greater percentage of filtered sodium and produce a dose dependent diuresis throughout their clinical dosage range.
They produce kaliuresis by increasing the exchange of sodium and potassium in the late distal tubule and collecting duct.
They increase magnesium and calcium excretion by reducing the reabsorption of these ions in the ascending limb by way of inh Na+K+2Cl- symporter. They cause a reduction of potassium back diffusion, and this increases magnesium and calcium excretion.
Loop diuretics - Clinical use
Pulmonary edema(iv)
Preferred diuretics in the treatment of persons with renal impairment (creatinine clearance <30mL/min)
Edema caused by heart failure, cirrhosis.
Hypertension(but thiazide drugs are more preferred)
Hypercalcemia
Loop diuretics - Adverse effects
Hypokalemia --> metabolic alkalosis Hypocalcemia hypomagnesemia Hyponatremia Hyperuricemia Hyperglycemia Hyperlipidemia Ototoxicity; tinnitus, ear pain, vertigo and hearing deficits. Blood cell deficiencies Hypersensitivity reactions
Loop diuretics - Interactions
Diuretic effect decreased by NSAIDs. Adm with ACE inh may cause excessive hypotension
Which loop diuretic has the highest incidence of ototoxicity?
Ethacrynic acid
Potassium-Sparing Diuretics
Amiloride
Triamterene
Spironolactone
Eplerenone
Potassium-Sparing Diuretics - Interactions
Adm with ACE inh or potassium –> hyperkalemia
Adm with NSAIDs –> renal failure
Amiloride - MoA
Blocking the entry of sodium into the principal tubular cells of the late distal tubule and collecting duct, these drugs prevent sodium reabsorption at this site and indirectly reduce the secretion of potassium into the tubular filtrate and urine. They produce a modest amount of natriuresis but decrease kaliuresis.
Amiloride - Clinical use
Treat hypokalemia induced by thiazide and loop diuretics
Amiloride - Adverse effects
Hyperkalemia
Blood cell deficiencies
GI distress